Former Port Washington Wisconsin Post Office

I need you help with this one. When I was visiting in September of 2013 we were walking around town. I didn’t even known about this one. In fact It was my fiancé who pointed it out to me.

Sine the existing post office was building in the late 1930’s this one has to be older than 1938 or so. What else can you tell me about this one? It appears to part of the bank now, but because it was a weekend, I don’t remember it being open.